Polymers based on the reaction of hydroxyl-containing vinyl monomers, such as the hydroxyl acrylates, with lactones are known. Because of their good film-forming and other characteristics, these polymers are becoming fairly widely accepted in industry. Specifically,
Sampson et al, U.S. Pat. No. 3,892,714 discloses hydroxy copolymers reacted with a lactone and, thereafter, crosslinked with a polyisocyanate. According to the patent disclosure, ethylenically unsaturated monomers, at least one containing hydroxyl groups, are polymerized in the presence of a solvent. The solvent preferably should not contain hydroxyl groups. Thereafter, a lactone is reacted with the resultant hydroxyl-containing polymer in the presence of a catalyst and solvent.
Fisk et al, U.S. Pat. No. 4,082,816 discloses caprolactone-modified acrylic polymers obtained by polymerizing a mixture of vinyl monomers, at least one monomer containing a carboxyl or hydroxyl group, with caprolactone. The reaction is carried out in the presence of a free radical catalyst and a Lewis acid catalyst in the presence of a solvent.
The Journal of Coatings Technology, Vol. 54, No. 693, October 1982, at page 77, in an article by Theodore et al entitled "Modification Of Acrylic Polymers For High Solids Coatings," discloses the reaction of a hydroxyl acrylic polymer with epsilon-caprolactone. According to the article, the hydroxyl-containing acrylic polymer is reacted with the lactone in the presence of a solvent and dibutyltin oxide catalyst.
Aldinger et al, U.S. Pat. No. 4,368,320 discloses acrylic or methacrylic resins containing hydroxyl groups modified with epsilon-caprolactone. In the formation of the resins, an adduct of a hydroxyalkylacrylate or methacrylate and epsilon-caprolactone is formed in a first step, and then in a second step the intermediate product is further copolymerized with acrylic acid or methacrylic acid esters and optionally vinyl aromatics in a suitable varnish solvent.
Weber, Jr. et al, U.S. Pat. No. 4,504,635 discloses a process where a monomer is formed from, for example, a hydroxyethyl acrylate and a lactone. This monomer is further reacted in the presence of a catalyst and solvent, for example with a diacrylate and optionally additional lactone.
According to the all of the aforesaid disclosures, the reaction products are formed in the presence of a solvent and a catalyst. Before the products can be used, for example, in the formation of crosslinked thermosetting resins of the type used in coating compositions, it is often necessary to remove the solvent. Additionally, since the products are prepared in a solvent medium, the equipment used in the polymer-forming process can be relatively complex. Therefore, there are distinct advantages to preparing the polymer in the bulk, if possible.
In a commonly assigned, related concurrently filed application Ser. No. 186,266 of Kathleen J. Bixler, Lisa M. Kessler, Kevin M. Scholsky, and Robert W. Stackman entitled "Bulk Process For Producing Cyclic Ester-Modified Polymers Without Use Of Catalyst," there is described a bulk process for producing cyclic ester-modified polymers in the absence of a catalyst. The products of that application have enhanced characteristics in relation to polymers produced in the presence of a solvent and with the prior art catalysts. The reaction, however, in the absence of a catalyst while being practical for most applications is relatively slow and requires temperatures, depending upon the component selected, of up to about 300.degree. C. An advantage would be obtained, therefore, if the reaction rates could be increased and at lower temperatures provided this was accomplished without adversely affecting the film-forming characteristics of coating compositions containing the products of the invention due to the presence of ionic species.